1. Field of the Invention
The present invention relates generally to substrate cleaning and drying, and more specifically to techniques, systems, and apparatus for preventing fluid deposit and accumulation on substrate surfaces during fabrication processes involving substrates such as a semiconductor wafer, a hard disk, a Liquid Crystal Display (LCD), or a Flat Display Panel (FDP).
2. Description of the Related Art
In a manufacturing processes for fabricating a semiconductor device, an LCD, a magnetic disk, an FDP, etc., there is a need to perform wet cleaning of substrates at various stages of the fabrication process. By way of example, integrated circuit devices are typically manufactured in the form of multi-level structures. At the substrate level, transistor devices having diffusion regions are formed over and into silicon substrates. In subsequent levels, interconnect metallization lines are patterned and electrically connected to the transistor devices to define the desired functional device. As is well known, patterned conductive layers are insulated from other conductive layers by dielectric materials, such as silicon dioxide. At each metallization level there is a need to planarize metal or associated dielectric material. In some applications, metallization line patterns are defined in the dielectric material, and then chemical mechanical planarization (CMP) operations are performed to remove excess metallization.
Following each CMP operation, a wet clean of the substrate is typically performed. The wet clean is designed to wash away any by-products of the fabrication process, remove contaminants, and to achieve and maintain the necessary degree of cleanliness essential to proceed to a subsequent fabrication operation. As transistor device structures become smaller and more complex, the precision required to achieve and maintain structure definition demands exacting standards of cleanliness be maintained in all process operations. If a wet clean is incomplete or ineffective, or if a post-wet clean drying is incomplete or ineffective, then unacceptable residue or contaminants are introduced into the processing environment, potentially comprising the integrity of the devices being fabricated.
Several substrate drying operations and techniques are employed for post-wet clean and other substrate drying, and include such processes as spin drying and the plurality of spin drying variations, configurations, and techniques. In a typical spin dry process, a liquid rinsing or cleaning agent, with or without a surface tension reducing drying agent, is applied to and removed from the surface of a substrate by spinning the substrate and using centrifugal force to dry the substrate.
FIG. 1 illustrates surface removal of fluids from a substrate 10 using a spin dry technique. The typically horizontally oriented substrate 10, having both an active surface and a backside surface to be spun dry, is positioned in a spin/dry, or a spin-rinse-dry (SRD) apparatus having one or more fixed edge wheels 12, and a stabilizer edge wheel 14. Substrate 10 is rotated 16 resulting in rinsing and drying agents, liquids, or any other fluids being driven from the surfaces of the substrate 10 by centrifugal force as indicated by fluid flow directional arrows 18.
Although such drying techniques as spin drying and Marangoni/Spin drying are generally effective for substrate drying, a notable exception to this effectiveness exists at the substrate edge. As fluids are driven 18 from the surface of the substrate 10, some fluid can be captured and trapped in fixed edge wheels 12 and stabilizer edge wheel 14, and re-deposited along edge of substrate 10 as it is spun.
Due to the exacting requirements of current and evolving substrate fabrication processes, complete and effective drying is highly desirable, but rarely achieved with current apparatus and techniques. What is needed are systems, techniques, and apparatus for complete and effective edge drying of substrates which eliminate the accumulation and re-depositing of fluids on a substrate edge.